Electromagnet valve, in particular for automatic gearboxes

ABSTRACT

The invention proposes a solenoid valve ( 10 ), in particular for automatic transmissions of motor vehicles. Solenoid valves ( 10 ) have the problem of vibrations that detract from shifting comfort. Integrating a throttle restriction ( 52 ) into the solenoid valve ( 10 ) at the end oriented toward the consumer as proposed by the invention makes it possible to efficiently reduce such vibrations. In addition, the production costs are low, in particular because the throttle restriction ( 52 ) is provided in a filter cage ( 44 ) of the solenoid valve ( 10 ).

PRIOR ART

[0001] The invention is based on a solenoid valve, in particular forautomatic transmissions, according to the preamble of claim 1, as isknown, for example, from DE 197 33 660 A1.

[0002] In the hydraulic control of automatic transmissions, the problemarises that hydraulic vibrations can occur, which detract from theshifting comfort and shorten the service life. It is possible to reduceor even prevent the occurrence of these vibrations among other things bymeans of throttle restrictions in the form of apertures placed betweenthe hydraulic actuators. Apertures between pressure regulators andfollower valves are particularly suitable means for these vibrations.These apertures are usually accommodated structurally somewhere in thelines between the pressure regulator and the consumer or in a so-calledintermediate plate. The apertures are usually provided in a positiondetermined based on structural circumstances, between the pressureregulator and a follower valve, in a passage through an intermediateplate.

ADVANTAGES OF THE INVENTION

[0003] The solenoid valve according to the invention, in particular foran automatic transmission, with the features of claim 1, has theadvantage over the prior art that a throttle restriction is provided ina simple manner by being integrated into the solenoid valve. Theposition of the throttle restriction relative to the solenoid valve isunambiguously established due to its integration into the solenoid valveso that it is placed at the position of its greatest effectiveness,which reduces application costs for the manufacturer of the hydrauliccontrol system.

[0004] It is particularly useful to provide the throttle restriction inthe consumer connection or working pressure connection of a filter cageof the solenoid valve. For technical manufacturing reasons, the throttlerestriction is particularly easy to produce at this location.

[0005] The filter cage produces a seal between the pressure chamber inwhich the working pressure is generated inside the solenoid valve and areceiving bore for the solenoid valve. An oil exchange can only occurvia the integrated aperture. It is very easy to adapt the losscoefficient of the throttle restriction to the given requirements bychanging its diameter and length.

[0006] Integrating the throttle restriction into the filter cage reducesthe cost of the entire system since the throttle restriction is lessexpensive to produce in the filter cage than in an intermediate plate.

[0007] Since the effectiveness of the throttle restriction in the filtercage depends on the relative position or distance from the solenoidvalve, the placement of the throttle restriction according to theinvention allows its diameter to be selected as larger than in anintermediate plate. This gives it a decisive functional advantage at lowtemperatures since this shortens the so-called step response times.

[0008] Alternatively, the throttle restriction can also be integrateddirectly into the connection fitting or flange of the solenoid valve.

[0009] Another advantage of the solenoid valve according to theinvention is that as part of the development and manufacturing process,it can be tested together with the throttle restriction that exerts apowerful influence on the valve hydraulics, a combined testing thatresults in a perceptible quality improvement.

[0010] A special shaping of the throttle restriction (e.g. step-shaped,conical, etc.) in order to optimize the dynamic behavior is easier toproduce through the plastic injection-molding technique of the filtercage than it is to produce in an intermediate plate by means of astamping or drilling tool.

[0011] There are other possible applications in which the orientation ofthe throttle restriction in the circumference direction is crucial foroptimizing the functioning of the throttle restriction. In such cases,the filter cage and the valve part can be provided with a rotationprevention means.

[0012] Other advantages and advantageous modifications of the inventionensue from the dependent claims and the description.

DRAWING

[0013] An exemplary embodiment of the invention is shown in the drawingand will be explained in detail in the description that follows.

[0014] The sole FIGURE shows a longitudinal section through a solenoidvalve.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0015] The sole FIGURE shows a solenoid valve 10, in particular for usein automatic transmissions of motor vehicles. In the current exemplaryembodiment, the solenoid valve 10 is used as a pressure regulating valvefor controlling actuators in automatic transmissions. Alternatively, itcan also be an electromagnetically pilot-operated valve.

[0016] The solenoid valve 10 has a magnet part 12 and a valve part 14disposed flush with it. The magnet part 12 essentially includes housing16, a coil 18, and a movable armature 20 that contains an armature rod22.

[0017] The valve part 14 is connected to the magnet part 12 by means ofa connection fitting 24. In addition to the connection fitting 24, thevalve part 14 also has an actuating element 26 and a ball-shaped closingelement 28. The connection fitting 24 is provided with an inlet 30, areturn 32, and a consumer connection 34. The armature 20 causes theactuating element 26 to move. The closing element 28 is situated insidethe inlet 30 and is actuated by a tappet 36 disposed inside theactuating element 26. The tappet 36 acts on the closing element 28 byreaching through a bore 38 provided between the inlet 30 and a pressurechamber 40 of the consumer connection 34, in which the working pressureis generated inside the solenoid valve 10. Inside the pressure chamber40, the tappet 36 passes through a baffle plate 41. The tappet 36extends further through the pressure chamber 40 and a bore 42 providedbetween the pressure chamber 40 and the return 32, and is finallyfastened inside the actuating element 26. The actuating element 26 canopen and close the bore 42.

[0018] A filter cage 44 is provided on the valve part 14. The filtercage 44 is essentially cup-shaped; the filter cloth 48 is placed at thebottom 46 and the annular wall 50 seals off the pressure chamber 40except for a throttle restriction 52, for example in the form of anaperture, provided in the wall 50. The throttle restriction 52 isintegrated into the filter cage 44 and consequently into the solenoidvalve 10. This offers advantages with regard to the precision of thedamping action and that of the manufacture. The fact that the throttlerestriction 52 is integrated into the solenoid valve 10, not spacedapart from it by a distance that varies according to structural dictatesas a function of the different installation positions, permits bettercontrol of the damping action. Since the filter cage 44 is a plasticinjection-molded part, the throttle restriction 52 can easily beprovided during manufacture.

[0019] Alternatively, it is also possible to integrate the throttlerestriction 52 into the pressure chamber of the valve part 14. As in thecurrent exemplary embodiment, with a solenoid valve 10 that is embodiedas a plastic injection-molded part with a correspondingly embodied slidevalve, this integration can be achieved during manufacture. It is alsopossible for the throttle restriction 52 not to be provided in thefilter cage 44 itself. For example, if a filter cage 44 is not required,then with the solenoid valve 10, the throttle restriction 52 can beintegrated into a sleeve that is placed around the pressure chamber 40.

[0020] The filter cage 44 or alternatively a sleeve is fastened to thevalve part 14 in a rotationally fixed manner. To this end, a projection54 is provided on the filter cage 44 or alternatively on the sleeve, anda corresponding recess 56 is provided on the valve part 14. However, arecess can also be provided on the filter cage 44 or alternatively onthe sleeve. The projection 54 can, for example, be embodied as a lug orrib and the recess can be embodied as a depression or groove. However,other possibilities for preventing rotation are also conceivable.

[0021] The throttle restriction 52 has a diameter of approx. 1 mm, andthe length is somewhat shorter than this. However, it is possible to useexperimentation, for example, to determine the optimal ratio of lengthto diameter for each intended application. In addition, it is notabsolutely necessary for the throttle restriction 52 to have a roundcross section. Conical and stepped diametrical progressions are alsoconceivable. It is important that the throttle restriction 52 beintegrated into the solenoid valve 10 at the end oriented toward theconsumer.

1. A solenoid valve (10), in particular for automatic transmissions,characterized in that a throttle restriction (52) is integrated into thesolenoid valve (10) at the end oriented toward the consumer.
 2. Thesolenoid valve (10) according to claim 1, characterized in that thethrottle restriction (52) is provided in a filter cage (44) of thesolenoid valve (10).
 3. The solenoid valve (10) according to claim 2,characterized in that the throttle restriction (80) is provided in awall (50) of the filter cage (44) that encompasses a pressure chamber(40) of the solenoid valve (10).
 4. The solenoid valve (10) according toclaim 1, characterized in that the throttle restriction (52) is providedin a sleeve that is placed around the pressure chamber (40).
 5. Thesolenoid valve (10) according to one of claims 2 to 4, characterized inthat a rotation prevention means is provided on the valve part (14) andon the filter cage (44) or sleeve.
 6. The solenoid valve (10) accordingto claim 5, characterized in that in order to prevent rotation, aprojection (54) is provided on the valve part (14) and a correspondingrecess (56) is provided in a filter cage (44) or sleeve, or vice versa.7. The solenoid valve (10) according to claim 1, characterized in thatthe throttle restriction (52) is integrated into the pressure chamber(40) of the solenoid valve (10).